Elsevier

Phytochemistry

Volume 55, Issue 3, October 2000, Pages 237-240
Phytochemistry

Absolute configuration and tautomeric structure of xylindein, a blue–green pigment of Chlorociboria species

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Abstract

The S absolute configuration of both chiral centers of xylindein was assigned using X-ray crystallographic heavy atom analysis after its conversion to a synthetic derivative. Crystallographic analysis of xylindein crystallized with phenols revealed that the proposed structure is the proper tautomer in the crystals.

Introduction

Xylindein (1) is a blue–green pigment previously isolated from the fungi Chlorociboria aeruginosa and aeruginascens (reviews: Blackburn et al., 1965, Edwards and Kale, 1965, synthetic studies: Giles et al., 1979, Giles et al., 1990). Since these fungi are widely distributed and their fruiting bodies and the infected wood assume a beautiful blue–green color, the characteristic pigmentation has attracted attention for over 2 centuries. The insolubility of 1 in common organic solvents had prevented its isolation and structure determination; however, this was overcome by Liebermann and Fischer in 1874 who obtained crystals by extracting the green wood with aqueous phenol. After extensive work by many chemists, the planar structure of the extended quinone was independently revealed in 1965 by Blackburn et al. and Edwards and Kale, through chemical derivatization and spectroscopic analyses. We reinvestigated the xylindein structure to reveal its hitherto-unknown absolute configuration and its tautomeric structure.

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Results and discussion

The fruiting bodies of the Chlorociboria species and the infected wood were collected from the Okutama mountain system. Xylindein (1) was extracted from infected wood with hot chloroform (Edward and Kale, 1965). In order to determine the absolute configuration of 1 by X-ray crystallographic analysis using the anomalous scattering effect of a heavy atom, the conversion of 1 to an appropriate derivative containing some heavy atoms was examined. The direct introduction of some alkyl groups

General

Melting points are uncorrected. Optical rotations were measured on a JASCO DIP-360 polarimeter. UV spectra were recorded on a HITACHI U-2001 spectrometer. IR spectra were recorded on a JASCO FT-IR-200 spectrometer as a KBr pellet or on an NaCl cell with nujol. 1H and 13C NMR spectra were recorded on a JEOL Lambda-300 (300 and 75 MHz, respectively) spectrometer. The chemical shifts were reported as δ values in ppm relative to TMS as an internal standard, unless otherwise stated. Low and high

References (6)

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    The structure of xylindein

    Tetrahedron

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    Xylindein Chimia

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  • R.G.F. Giles et al.

    A quinonoid naphthopyranone as a model for the synthesis of the pigment xylindein. Photochemical formation of the lactone ring

    South African Journal of Chemistry

    (1979)
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